Design of partially grouted reinforced masonry shear walls in an earthquake-prone area: Proposal based on the LRFD approach

Abstract

There is a lack of reliability assessment of modern structural masonry design. Hence, a novel reliability-based calibration of the in-plane shear ultimate limit state for partially grouted reinforced masonry shear walls (PGRMSWs) is presented. This calibration allows for the proposal of a load and resistance factor design (LRFD) methodology oriented to in-plane shear design, responding to the need to update the reinforced masonry Chilean code, which is currently based on the allowable stress design (ASD) format. An extensive database of material and assembly tests and numerical research that made this code update proposal feasible are summarized. The reliability-based calibration was performed aiming to define a target reliability index (β_T) and the corresponding strength reduction factors (φ) were recommended. A value of β_T = 2.5 is defined based on the reliability analysis of representative existing structures against earthquake-induced shear force. The results allow for recommending φ = 0.60 for walls made of multi-perforated clay bricks and φ = 0.70 for walls made of hollow concrete blocks. Additionally, φ = 0.85 and φ = 0.65 are recommended for flexural and axial strength of compression-controlled walls by adapting international standards to Chilean practice. Comparisons of the required horizontal reinforcement between ASD and LRFD methodologies are presented for a 4-story case study building. The results show that the total reinforcement quantities from ASD and LRFD methodologies are similar, which means the proposal does not imply a more restrictive and expensive design; yet, the LRFD proposal provides designs with a uniform reliability level across various load scenarios.